1. Field of the Invention
This invention relates to lens barrier apparatuses, and more particularly, to a lens barrier apparatus located at a front face of a lens body tube so as to protect an image pickup lens.
2. Description of the Related Art
Conventionally, there have been cameras with the lens barrier function to protect the lens from dust or the like entering from the outside. Generally, the lens barrier is integrally formed at a front face side of a lens body tube, and protects the lens in the lens body tube, for example, by closing sectors (blades) swingably provided. For instance, Japanese Patent Application Publication No. 3-186828 discloses a shutter apparatus having a lens barrier, and proposes a technique of driving the sectors for the shutter or lens and driving the lens barrier by means of one actuator. The lens barrier of the shutter apparatus has a configuration in which the lens barrier is moved through a pinion, gear, cam, and actuating lever.
The lens barrier of Japanese Patent Application Publication No. 3-186828 has a configuration in which a motor for driving the sectors for the shutter or the lens is also used for driving the barrier (sector), and a drive power of the motor is transmitted through a gear train, cam, and actuating lever to the lens barrier. In addition, the actuating lever is biased in a direction of closing the sector. When the cam rotates, the actuating lever is driven in accordance therewith. Then, the lens barrier is swung to form a closed or open state.
In the above configuration, if the biasing force of the actuating lever is set too strong, the rotation of the cam will be impeded and the load on the motor will be increased. On the other hand, if the biasing force of the actuating lever is weak, the lens barrier will not be retained stably at a closed position thereof. As stated heretofore, it is difficult to swing the lens barrier stably by use of only the biasing force of the actuating lever. If the state of the lens barrier is unstable at a closed position, the lens barrier will be brought to a half-open state when an impact is externally applied. This will permit dust or the like to enter the inside and the lens cannot be protected in the lens body tube with certainty.
For the above reason, a stopper mechanism may be provided separately in order to prevent the unstable movement of the lens barrier. An example of the stopper mechanism is to stop the actuating lever of the lens barrier at a stop position. However, once there is provided such stopper mechanism, the configuration will be complicated and the apparatus will be increased in size. Alternatively, the motor may be energized to keep the position of the cam at a fixed position; however, the power consumption will be increased in this case.